The present invention is directed to a prosthetic foot, and more particularly, to a prosthetic foot that provides both angular and anterior-posterior lateral adjustability with respect to the upright assembly coupled thereto.
A prostheses is often used to replace and amputated portion of a limb and help to restore the amputee's ability to use that limb. A prostheses for a lower extremity amputation will often include an artificial foot connected to an upright assembly (pylon, tube or shaft) which is in turn connected to a custom fitted socket assembly. If the amputation is above the knee, the upright assembly will commonly include an artificial knee joint.
U.S. Pat. No. 5,529,576 discloses a prosthetic foot having a pyramidal link plate mounted within a recess extending into a proximal end of the prosthetic foot. While the pyramidal link plate, in conjunction with the annular socket component coupled to the distal end of the upright assembly, allows for angular adjustments of the upright assembly with respect to the prosthetic foot, this coupling does not provide for any translational adjustments.
While some prosthetists believe that such angular adjustability alone provides sufficient versatility to the prosthetic limb so as to allow the prosthetists to adjust and control heel strike and heel compression of the prosthetic limb, other prosthetists believe that upright assemblies that are substantially angled with respect to the prosthetic foot will adversely affect ground reaction forces during gate. In this case, once the prostheses is aligned, the prosthetists will often prefer to "transfer" the socket and foot to a fixture and thereafter realign the prosthetic components between the socket and the foot to achieve pylon verticality.
Additionally, regardless of the angle of the upright assembly, it is also sometimes desirable to provide for translational adjustment or alignment versatility of the prosthetic foot with respect to the prosthetic limb. Such anterior-posterior translation will affect the patient's and prosthetist's ability to control heel strike and heel compression in modern prosthetic feet. For example, when an energy storing foot is used, when the upright assembly is slid in the posterior direction with respect to the prosthetic foot, this adjustment results in a longer lever arm for toe-off at midstance. In the contrary, when the upright assembly is slid in the anterior direction with respect to the prosthetic foot, this adjustments results in a short lever arm for toe-off at midstance, which in turn means that this alignment may be more stable for a new amputee.
U.S. Pat. No. 4,636,220 discloses a prosthetic foot that provides for heel height adjustment of the foot. The prosthetic foot includes a cavity in the keel of the foot which is shaped and sized to receive a bolt-block extending distally from pylon component of the prosthetic limb. An arcuate rail component is secured to the distal end of the bolt block; and the arcuate rail component engages an arcuate groove and track component securing to the upper surface of the cavity in the foot. Apertures are provided in both the arcuate rail component and the arcuate groove component, and a threaded bolt extends upwardly through the apertures and into a threaded bore in the bolt block. Upon tightening the bolt, the arcuate rail component is fixedly wedged within the arcuate groove component to firmly retain the bolt block in a fixed position within the cavity. To adjust the heel height (vertical/angular adjustment), the bolt is loosened, the arcuate rail is slid forward or backward within the groove depending upon the desired adjustment, and then the bolt is tightened again when the arcuate rail and bolt block are in the desired orientation. A disadvantage of this system is that the design dictates that lateral adjustments must occur with the vertical/angular adjustments--independent lateral or vertical/angular adjustments are not provided. Further, to make such adjustments with this system, the cosmetic cover of the prosthetic limb must be removed after each adjustment to maintain pylon verticality. Finally, this system requires a specially designed prosthetic foot and is not capable of being used on conventional, industry standard, prosthetic foot components.
Accordingly, there is a need for a prosthetic foot interconnection assembly which provides for independent lateral and angular adjustments; which allows for independent translational adjustments, yet which in turn, does not adversely affect the pylon verticality; which provides for lateral adjustments, especially anterior-posterior adjustments; which does not require that the prosthetic limb be disassembled or even removed from the patient's residual limb during or before adjustment; which is easy to assemble and adjust; which may be used with conventional, industry standard, prosthetic foot components; and which is relatively easy and inexpensive to manufacture.